Expose flake interface that does not rely on overlays

.github/dependabot.yml

@@ -0,0 +1,10 @@
+version: 2
+updates:
+  - package-ecosystem: "gomod"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

docs/getting-started.md

@@ -63,7 +63,7 @@ pkgs.buildGoApplication {
 
 The quickest way to get started if using Nix Flakes is to use the Flake template:
 ``` bash
-$ nix flake init -t github:tweag/gomod2nix#app
+$ nix flake init -t github:nix-community/gomod2nix#app
 ```
 
 ## Basic usage

flake.nix

@@ -2,10 +2,9 @@
   description = "Convert go.mod/go.sum to Nix packages";
 
   inputs.nixpkgs.url = "github:NixOS/nixpkgs/master";
+  inputs.flake-utils.url = "github:numtide/flake-utils";
 
-  inputs.utils.url = "github:numtide/flake-utils";
-
-  outputs = { self, nixpkgs, utils }:
+  outputs = { self, nixpkgs, flake-utils }:
     {
       overlays.default = import ./overlay.nix;
 
@@ -18,19 +17,33 @@
       defaultTemplate = self.templates.app;
 
     } //
-    (utils.lib.eachDefaultSystem
+    (flake-utils.lib.eachDefaultSystem
       (system:
         let
-          pkgs = import nixpkgs {
-            inherit system;
-            overlays = [
-              self.overlays.default
-            ];
+          pkgs = nixpkgs.legacyPackages.${system};
+
+          # The current default sdk for macOS fails to compile go projects, so we use a newer one for now.
+          # This has no effect on other platforms.
+          callPackage = pkgs.darwin.apple_sdk_11_0.callPackage or pkgs.callPackage;
+
+          inherit (callPackage ./builder {
+            inherit gomod2nix;
+          }) mkGoEnv buildGoApplication;
+          gomod2nix = callPackage ./default.nix {
+            inherit mkGoEnv buildGoApplication;
           };
         in
         {
-          packages.default = pkgs.callPackage ./. { };
-          devShells.default = import ./shell.nix { inherit pkgs; };
+          packages.default = gomod2nix;
+          legacyPackages = {
+            # we cannot put them in packages because they are builder functions
+            inherit mkGoEnv buildGoApplication;
+            # just have this here for convenience
+            inherit gomod2nix;
+          };
+          devShells.default = callPackage ./shell.nix {
+            inherit mkGoEnv gomod2nix;
+          };
         })
     );
 }

overlay.nix

@@ -1,7 +1,7 @@
 final: prev:
 let
-  # The newer Darwin SDK does not exist in current (nixos-22.05) stable
-  # branches, so just fallback to the default callPackage.
+  # The current default sdk for macOS fails to compile go projects, so we use a newer one for now.
+  # This has no effect on other platforms.
   callPackage = final.darwin.apple_sdk_11_0.callPackage or final.callPackage;
 in
 {

shell.nix

@@ -8,14 +8,16 @@
       ];
     }
   )
+, gomod2nix ? pkgs.gomod2nix
+, mkGoEnv ? pkgs.mkGoEnv
 }:
 
 pkgs.mkShell {
   NIX_PATH = "nixpkgs=${builtins.toString pkgs.path}";
   nativeBuildInputs = [
     pkgs.nixpkgs-fmt
     pkgs.golangci-lint
-    pkgs.gomod2nix
-    (pkgs.mkGoEnv { pwd = ./.; })
+    gomod2nix
+    (mkGoEnv { pwd = ./.; })
   ];
 }

templates/app/default.nix

@@ -9,9 +9,10 @@
       ];
     }
   )
+, buildGoApplication ? pkgs.buildGoApplication
 }:
 
-pkgs.buildGoApplication {
+buildGoApplication {
   pname = "myapp";
   version = "0.1";
   pwd = ./.;

templates/app/flake.nix

@@ -4,20 +4,26 @@
   inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
   inputs.flake-utils.url = "github:numtide/flake-utils";
   inputs.gomod2nix.url = "github:nix-community/gomod2nix";
+  inputs.gomod2nix.inputs.nixpkgs.follows = "nixpkgs";
+  inputs.gomod2nix.inputs.flake-utils.follows = "flake-utils";
 
   outputs = { self, nixpkgs, flake-utils, gomod2nix }:
     (flake-utils.lib.eachDefaultSystem
       (system:
         let
-          pkgs = import nixpkgs {
-            inherit system;
-            overlays = [ gomod2nix.overlays.default ];
-          };
+          pkgs = nixpkgs.legacyPackages.${system};
 
+          # The current default sdk for macOS fails to compile go projects, so we use a newer one for now.
+          # This has no effect on other platforms.
+          callPackage = pkgs.darwin.apple_sdk_11_0.callPackage or pkgs.callPackage;
         in
         {
-          packages.default = pkgs.callPackage ./. { };
-          devShells.default = import ./shell.nix { inherit pkgs; };
+          packages.default = callPackage ./. {
+            inherit (gomod2nix.legacyPackages.${system}) buildGoApplication;
+          };
+          devShells.default = callPackage ./shell.nix {
+            inherit (gomod2nix.legacyPackages.${system}) buildGoApplication mkGoEnv gomod2nix;
+          };
         })
     );
 }

templates/app/shell.nix

@@ -9,14 +9,16 @@
       ];
     }
   )
+, mkGoEnv ? pkgs.mkGoEnv
+, gomod2nix ? pkgs.gomod2nix
 }:
 
 let
-  goEnv = pkgs.mkGoEnv { pwd = ./.; };
+  goEnv = mkGoEnv { pwd = ./.; };
 in
 pkgs.mkShell {
   packages = [
     goEnv
-    pkgs.gomod2nix
+    gomod2nix
   ];
 }